This invention relates to an axial blower, particularly for cooling the condenser which is part of an air conditioner associated with an automotive vehicle and which is situated at the vehicle radiator. The blower has an electric motor whose motor shaft carries a hub of a blower wheel. The hub is affixed to the output end of the motor shaft by a bell-shaped member which is carried by the hub, and which surrounds that part of the motor housing which is oriented towards the output end of the motor shaft. The hub surrounds the housing end which is oriented towards the free shaft end (output end). The blower has vane-like ribs in the hub on that side which is oriented toward the blower wheel, so that the hub, by virtue of its rotation, causes cooling air to flow through the electromotor through ventilating openings in the front bearing cover (lid) to air outlet openings in the rear bearing cover. It is noted that the "front" of the motor housing, as well as the "front" bearing cover is assumed to be situated at the output end of the motor shaft, while the "rear" of the motor housing, as well as the "rear" bearing cover is assumed to be located at the opposite end of the output shaft. The heated cooling air which exits the air outlet openings is guided into the ambient atmosphere through the intermediate space between the outer circumferential surface of the motor housing of the electromotor and the inner ribbed circumferential surface of the hub at the front bearing cover.
Blower manufacturers are compelled to supply very compact and high-efficiency blower units for the cooling of condensers in air conditioners of automotive vehicles, based on customer-required parameters relating to structural volume and output. The structural length available in the vehicle between the front grill and the condenser/cooling unit admits an impeller wheel only of the type which covers the drive motor along its entire length. Further, it is a requirement that the waste heat generated by the high supply voltage at high ambient temperatures has to be securely removed from the electromotor by its own ventilation system.
Axial blowers of the above-outlined type are thus known in which the hub of the blower impeller wheel is bell-shaped, it surrounds the electromotor and is fixedly connected with the end of the motor shaft by means of a support. It is a disadvantage of this arrangement that the bell-shaped hub surrounding the motor housing obstructs an intensive cooling of the motor. A cooling of the motor has been improved in the prior art by providing vane-like ribs on the hub oriented towards the impeller wheel. In this manner, during rotation of the impeller wheel there is effected a flow of coolant air through the electromotor through the ventilating opening in the front bearing cover to air outlet openings in the rear bearing cover, whereby the heated air which exits from the air outlet openings in the rear bearing cover is guided into the ambient atmosphere through the intermediate space between the outer circumferential surface of the motor housing of the electromotor and the inner ribbed circumferential surface of the hub at the front bearing cover.
Further, it is a disadvantage of the prior art that because of the relatively great axial length of the bell-shaped hub, at the two ends thereof imbalance phenomena appear which lead to an increased noise during operation.